Method for manufacturing treated grinding rods



June 7, 1966 A. L. BARD ETAL 3,

METHOD FOR MANUFACTURING TREATED GRINDING RODS Original Filed Oct. 16, 1961 2 Sheets-Sheet l INVENTORS ALBERT L. BARB AND WAYNE B. WEED,

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June 7, 1966 A. L. BARD ETAL 3,255,053

METHOD FOR MANUFACTURING TREATED GRINDING RODS Original Filed Oct. 16, 1961 2 Sheets-Sheet 2 INVENTOR ALBERT L. BARD AND WAYNE B WE BY ED, WM, 7W

ATTORNEYS United States Patent O 3,255,053 METHOD FOR MANUFACTURING TREATED GRINDING RODS Albert L. Bard and Wayne B. Weed, Independence, Mo., assignors to Armco Steel Corporation, Middletown, Ohio, a corporation of Ohio Original application Oct. 16, 1961, Ser. No. 145,251, now Patent No.-3,l70,641, dated Feb. 23, 1965. Divided and this application Sept. 16, 1964, Ser. No. 396,848

2 Claims. (Cl. 148-131) This invention relates to a method and apparatus for manufacturing heat treated grinding rods, and is a division of copending application Serial No. 145,251 filed October 16, 1961, now Patent No. 3,170,641, by the same inventors. Such grinding rods are used in rod mills which in recent years have become increasingly important as a comminuting device classified generally between fine crushing and coarse grinding. Thus, a rod mill has application as a fine crusher or as a coarse grinder. The output of a rod mill is then generally further comminuted as necessary in a ball mill which is classified as a fine grinder.

In connection with ball mills, the grinding balls have for many years been heat treated to harden them. Attempts have also been made to heat treat and harden grinding rods. The hardening of grinding rods, however, is beset by problems not encountered in connection with hardening grinding balls and therefore prior attempts to harden grinding rods have either been entirely unsuccessful or have produced a relatively low hardness.

The principal problem encountered is that if a grinding rod is subjected to a quenching treatment after heating in a furnace, the rod tends to Warp or bend. So long as the hardness does not exceed about 325 Brinell as taken with a mm. Hultgren Ball (35 on the Rockwell C Scale), such a rod can be machine straightened. If

attempts are made to harden to a higher hardness, such as for example 600 Brinell (60 on the Rockwell C Scale), it becomes impossible to maintain the hardness and straighten the rod. Either the rod will break or the rod must be materially softened in order to be straightened.

In the trade, the phrase commercial straightness means a deviation from the center line not greater than one-quarter inch per five feet of length. The term machine straight means a maximum lateral deviation of one-eighth inch in five feet. Any attempt to heat and quench a rod by previous methods will resultin a distortion much more than commercial straightness, and if a desired hardness is achieved, such a rod cannot be straightened. It must be borne in mind that rods commonly used in rod mills may vary from a diameter of three inches to four inches and have a length from ten to sixteen feet. They may weigh from about 240 pounds to about 700 pounds each.

With the foregoing considerations in mind, it is an object of the present invention to provide an apparatus for heat treating grinding rods and the like which will insure that they will be within machine straight tolerances after quenching. A further object of the invention involves a method for heat treating grinding rods to achieve the results outlined above.

These and other objects of the invention which will be pointed out in greater detail hereinafter or which will be apparent to one skilled in the art upon reading these specifications, are accomplished by that certain construction and arrangement of parts and by that series of method steps of which the following are exemplary embodiments.

Reference is made to the drawings forming a part hereof and in which:

FIGURE 1 is a fragmentary elevational view of an apparatus for quenching the rods after they have been heated in a furnace.

FIGURE 2 is an end elevational view as seen from the left end of FIGURE 1.

FIGURE 3 is a fragmentary plan view showing the arrangement of rollers for feeding and rotating and maintaining straight the grinding rods during the quenching operation.

FIGURE 4 is a somewhat diagrammatic view on a smaller scale similar to FIGURE 3, showing the relation of the feeding and rotating apparatus to the heating furnace.

FIGURE 5 is a fragmentary perspective view of the quenching rings and associated apparatus; and

FIGURE 6 is a cross-sectional view taken on the line 6-6 of FIGURE 5 on an enlarged scale.

The grinding rods of this invention are usually made of high carbon steel (.60 to 1.0% carbon) although it is within the scope of the invention to modify the analysis in known ways, if, for example, it is necessary to increase the hardenability of the steel.

Briefly, in the practice of the invention the rods are heated in a continuous furnace through which they are passed axially while being rotated, the speed of the rod through the furnace being such as to achieve in the rod a temperature of from about 1450 F. to about 1600 F. in order to austenitize the steel. It will of course be understood that any other means of heating such as rolling the rods across the hearth of a sloping type furnace could be used, so long as they produce a uniformly heated rod.

As the rod emerges from the furnace in the austenitic condition, it enters the quenching apparatus in which it passes through a series of annular nozzles through which a suitable quenching medium is caused to impinge upon the surface of the rod. As the rod passes through the quenching rings, it is caused to rotate about its axis and it is mechanically constrained to remain in straight condition.

The details of the temperature to which the rod is raised, the depth in from the surface to which the desired temperature penetrates, the temperature and character of the quenching medium, and the speed through the quenching apparatus do not constitute a part of the present invention and the details of the heat treatment are well known to those skilled in the art. By way of an example, however, a three-inch diameter bar was caused to move through the apparatus at a lineal speed of about twelve feet per minute and in the particular apparatus this meant that each element of the rod was subjected to a period of about eighty seconds in the quench. Such rods had a surface hardness in excess of 50 R If a higher or lower hardness is desired, the

heat treatment and quench may be modified as is well known to those skilled in the art.

Similarly, it will be understood that in a grinding rod as in a grinding ball it is desirable that the core be softer than the outer shell; It is desirable in a grinding rod having a surface hardness of 50 or above on the Rock- Well C Scale, that the core have a hardness of at least 35 on the Rockwell C Scale. The details of temperatures and times necessary to achieve these conditions are well known to those skilled in the art and will not be described further.

The. particular material of which the rods were made I 720 hours in the mill was 33.8% as against a weight loss after 720 hours of 47.1% with conventional grinding rods.

Referring now to the drawings, and particularly FIG- URE 4, the furnace is shown diagrammatically at 10 and the rod being treated is shown at 11. As the rod emerges from the furnace, it enters the quenching apparatus which comprises a series of pairs of interdigitated skewed rollers 12, 13, etc. In FIGURE 4, only the first two pairs are shown and only the first two pairs are shown in FIG- URE 3. In the particular embodiment of the machine shown in the drawings, a total of five pairs are used; but the number of pairs can be varied to accommodate rods of varying sizes. The rolls will of course be adjustable to change the helix angle for different diameter rods.

Since these pairs of rolls are interdigitated as clearly shown in FIGURES 3 and 4, they form what may be termed a two point support for the grinding rod 11 as best seen in FIGURE 2. All of the rolls of these pairs are driven in the same direction of rotation whereby the rod 11 supported thereon is caused to rotate about its axis. Because the pairs of rolls are skewed as clearly seen in FIGURES 2 and 3, they cause the rod to be fed axially in the direction of the arrow (FIG. 4) while it is being rotated.

In order to enforce upon the rod a straight condition during its passage through the quenching apparatus, there is associated with each pair of rolls 12, 13, etc. a third roll 12a, 13a, etc., and this roll is mounted to ride on top of the. rod 11 and it is strongly pressed against the rod by means of springs 12b, 131), etc. which urge the respective roll mounting member 17 downwardly. The rollers 12a, 13a, etc. are mounted on the members 17. The reason for the spring mounting is to permit use of the apparatus with grinding rods of diiferent diameters but it will be seen that the springs will exert a strong force to press the respective rolls 12a, 13a, etc. against the rods 11 as it passes through the apparatus. If necessary to insure a straight condition, this third roll may use a positive positioning means such as a screw in place of the spring.

Between the various pairs of rollers described above, there are disposed the quench rings 20. In the particular embodiment illustrated there are two quench rings 20 between each set of rollers.

The quench rings 20 are disposed so that the rod being treated may pass through them as perhaps best seen in FIGURE 5. There are two connections for quenching medium for each quenching ring as indicated at 21 and 22 in FIGURE and a valve 23 may be provided in each line. The connections 21 to the Various quench rings are connected to a header 24 and the connections 22 are connected to a header 25. These headers are connected, as best seen in FIGURES 1 and 2, to a suitable pump diagrammatically illustrated as being within the box 26 in FIGURES 1 and 2. Thus, each of the quench rings 20 is supplied with quenching medium at two diametrically opposite points. The quench ring itself, as best seen in FIGURE 6 and which may be made in two pieces 27,

28 provided with suitable sealing means as at 29 and bolted together, provides an annular space 30 connecting with the connections 21 and 22 so that the ring provides an annular conical nozzle through which a generally conical sheet of water emerges as indicated by the arrows 31 in FIGURE 6. Preferably, the direction of the conical annular sheet of quenching medium is such that it impinges against the surface of the rod 11 in the same direction as the direction of rod travel, except for the last quenching ring, which is reversed to stop the water from following the rod.

It will thus be clear that as the rod passes through the apparatus moving axially and rotated about its axis, it is subjected to a plurality of annular sheets of water or other quenching medium.

The various pairs of rollers 12, 13, etc. may be driven from a suitable prime mover or prime movers (not shown) by means of a sprocket chain or the like 40 engaging the sprockets 41 and 42. These sprockets, as shown, respectively drive the rollers of the first pair 12 through the connecting rods 43, 44, each of which is provided with a universal joint connection at each end. The second pair of skewed rollers 13 is then driven from the first pair12 through the connecting rods 45, 46, which again are provided with universal joints at each end, as clearly shown in FIGURE 3.

It will be clear that various modifications may be made without departing from the spirit of the invention and no limitations not specifically set forth in the claims are intended.

The invention having now been fully described, what is claimed and what it is desired to secure by Letters Patent The embodiments of the invention in which an exclusive property or privilege is claimed ar defined as follows:

1. The method of manufacturing machine straight abrasion resistant rods for rod mills, which includes the steps of passing a rod of high carbon steel through a furnace to heat the same to an austenitic condition, and then moving said rod axially out of said furnace along a straight path while rotating said rod about its axis, subjecting said rod during said axial and rotating movement to a quenching treatment, and mechanically enforcing upon said rod an axially straight condition during said axial and rotating movement and quenching treatment.

2. The method of claim 1, including the step of controlling the axial speed of said rod through said heating and quenching treatment to achieve a surface hardness of at least on the Rockwell C Scale.

References Cited by the Examiner UNITED STATES PATENTS 1,448,878 3/1923 Smith 148-131 X 1,570,815 1/1926 Wylie 148-130 X 2,049,830 8/1936 Bayless 148-12.4 2,333,344 11/1943 Smith et a1. 2666 2,570,883 10/1951 Stivin 148131 2,783,788 3/1957 Ungerer 148156 X 2,969,299 1/ 1961 Fullerton et al. 148-131 3,148,093 9/1964 Williamset a1. 148131 3,149,189 9/1964 Gogan 2666 3,169,893 2/1965 Wuerfel 148131 DAVID L. RECK, Primary Examiner. 

1. THE METHOD OF MANUFACTURING MACHINE STRAIGHT ABRASION RESISTANT RODS FOR ROD MILLS, WHICH INCLUDES THE STEPS OF PASSING A ROD OF HIGH CARBON STEEL THROUGH A FURNACE TO HEAT THE SAME TO AN AUSTENITIC CONDITION, AND THEN MOVING SAID ROD AXIALLY OUT OF SAID FURNACE ALONG A STRAIGHT PATH WHILE ROTATING SAID ROD ABOUT ITS AXIS, SUBJECTING SAID ROD DURING SAID AXIAL AND ROTATING MOVEMENT TO A QUENCHING TREATMENT, AND MECHANICALLY ENFORCING UPON SAID ROD AN AXIALLY STRAIGHT CONDITION DURING SAID AXIAL AND ROTATING MOVEMENT AND QUENCHING TREATMENT. 